1. Field of the Invention
The present invention relates generally to a two-way plug which can be inserted into a connection port regardless of the orientation of the plug so that connection terminals of the plug can be connected to connection pins of the connection port without shorting a circuit and, more particularly, to a two-way plug which includes a rectangular frame which is brought into contact with and supported by the inner surface of the connection port, so that the plug is prevented from being undesirably removed from the connection port by incidental external shock, and connection terminals of the plug can be stably maintained in a state of having been connected to the connection pins of the connection port for a long period of time.
2. Description of the Related Art
Various communication devices, such as PCs, MP3s, PDAs, digital cameras, cellular phones, etc., have recently been developed and marketed. Furthermore, data communication between such communication devices has increased.
To realize data communication between communication devices, connection ports are provided in the communication devices, and a cable having plugs provided on both ends thereof connects the communication devices to each other to allow data transfer therebetween when the plugs are inserted into the respective connection ports of the communication devices.
Generally, USB memory devices include a main body having memory, and a plug which is coupled to the main body such that one end of the plug is exposed out of the main body. The exposed end of the plug is inserted into and connected to the connection portion of a communication device. The other end of the plug is connected to the memory installed in the main body. Thereby, the plug facilitates data communication between the communication device and the memory of the USB memory device. When defined widely, memory is a kind of communication device.
Such a plug which facilitates data communication between communication devices includes a substrate and a plurality of connection terminals provided on the surface of the substrate.
To provide data communication, the connection terminals of the plug are connected to connection pins provided in the connection port into which the plug is inserted. In typical plugs, connection terminals are provided on only one surface of the substrate.
Thus, when a user inserts a typical plug into a connection port, he/she must pay attention to the orientation of the plug.
These days two-way plugs have been developed, and these do not require the user to pay attention to the orientation of a plug when it is inserted into a connection port. In such a two-way plug, connection terminals are arranged symmetrically on opposite surfaces of the substrate, so that regardless of the orientation of the plug when it is being inserted into the connection port, the connection terminals of the plug can be connected to connection pins of the connection port.
In detail, the connection pins which are connected to the connection terminals of the plug are provided in an upper (or lower) portion of the connection port. A tension pin is provided in a lower (or upper) portion of the connection port. The tension pin biases a substrate of the plug to the connection pins such that the connection pins are reliably connected to the connection terminals. The connection terminals are provided on each of opposite surfaces of the substrate. However, in the conventional two-way plug, when the connection terminals provided on one surface of the substrate are connected to the connection pins, the connection terminals provided on the other surface of the substrate may come into contact with the tension pin, thereby causing a short-circuit. Thus, the two-way plug typically includes a means for preventing short-circuiting.
Methods of prevent a short-circuit include a method that prevents the connection terminals from coming into contact with the tension pin using a mechanical structure and another method that uses a circuit. Techniques proposed in Korean Patent Registration No. 0626909 entitled “USB plug with two sides selectively connectable to USB port” and in Korean Patent Laid-open Publication No. 2006-65658 entitled “Electric connector” are representative examples of the method using the mechanical structure. An representative example of the method using the circuit was proposed in Korean Patent Laid-open Publication No. 2009-0120052 which was filed by the applicant of the present invention and entitled “Two-way plug equipped with circuit for preventing short-circuit”
The two-way plug of the present invention pertains to the method wherein a mechanical structure is used to prevent a short-circuit from being caused. In a manner similar to the technique of No. 2009-0120052, the two-way plug of the present invention includes a rectangular frame which surrounds a substrate, and the outer surface of the rectangular frame comes into contact with the inner surface of a connection port, thus preventing a short-circuit.
Generally, rather than the plug being easily inserted into the connection port without resistance, many users want to feel with their hand a slight contact resistance when the plug is inserted into the connection port, so that a user can perceive the insertion of the plug into the connection port and the connection of the connection terminals to the connection pins being made. Furthermore, users require that the plug be prevented from being undesirably removed from the connection port by an incidental external shock. The two-way plug having the rectangular frame can meet the requirements of the users.
FIG. 1 is a view showing the two-way plug, according to the conventional technique proposed in Korean Patent Laid-open Publication No. 2009-0120052. The plug 40 includes a rectangular frame 400, a substrate 401 which is disposed in the central portion of the rectangular frame 400, and connection terminals 403 which are provided on each of opposite surfaces of the substrate 401.
The substrate 401 comprises a flexible PCB. Thus, when the plug 40 is inserted into a connection port 100, the substrate 401 is bent when contact is made with a protruding plate 101 of the connection port 100 and it advances along the surface of the protruding plate 101. After this, the connection terminals 403 of the substrate 401 are connected to the connection pins 102 of the protruding plate 101.
However, in this conventional technique, there is a problem of low durability, making it difficult to use repetitively for a long period of time. The flexible PCB 401 is sufficiently elastic to be repeatedly bent, but the connection terminals 403 are formed on the flexible PCB 401 by plating metal, typically, copper, having low flexibility. Therefore, the thin connection terminals 403 which are applied on the surface of the flexible PCB 401 may crack after the flexible PCB 401 is bent a large number of times. If a crack occurs in a connection terminal 403, a defective connection between the connection terminal 403 and the corresponding connection pin 102 is induced, making the data communication unreliable.
In addition, there is a likelihood that after the flexible PCB 401 comes into contact with the protruding plate 101 of the connection port 100, it may not advance along the surface of the protruding plate 101 and thus may bend excessively at the position where it stops and break there. In the drawing, although the flexible PCB 401 is illustrated as being bent and advancing onto the surface of the protruding plate 101 which has the connection pins 102, there is a likelihood of the flexible PCB 401 being incorrectly bent and advanced onto the other surface of the protruding plate 101.
Moreover, in the conventional technique, the connection terminals 403 provided on one surface of the flexible PCB 401 are connected to the connection pins 102 provided on the protruding plate 101, and the connection terminals 403 provided on the other surface of the flexible PCB 401 come into contact with the inner surface of the rectangular frame 400. In other words, all the connection terminals 403 provided on opposite surfaces of the flexible PCB 401 come into contact with the connection pins 102 or the rectangular frame 400. Thus, frictional force on opposite surfaces of the flexible PCB 401 is increased, so that the flexible PCB 401 may not advance smoothly along the surface of the protruding plate 101. In contrast, if frictional force on opposite surfaces of the flexible PCB 401 is small (that is, if the gap between the flexible PCB 401 and the protruding plate 101 is comparatively large), the connection terminals 403 may not be reliably connected to the connection pins 102. Furthermore, if the connection terminals 403 or the connection pins 102 are worn after being used for a long period of time, the connection therebetween may become unstable.